Presently, nearly half of the transportation-related energy consumption is covered by oil. Electric cars are expected to proliferate because the proliferation of the electric cars will increase the proportion of coverage of energy consumption by the electricity generated by alternatives to oil, such as nuclear power and natural energy including wind power, solar power or the like that emit less carbon dioxide. Expectations are also placed on hybrid cars that use both a secondary battery and an engine to move the cars, because they can drastically reduce fuel consumption. As a hybrid car whose energy is covered by electricity by a larger ratio, a plug-in hybrid car mainly uses electric energy and uses gasoline as a sub energy, and seems to bridge to a complete electric car.
For charging an electric car, a commercial AC power supply from an electric power system is used, and since infrastructure of electric feeder is already facilitated to each home, charging is possible anywhere. At each home garage, charging of these secondary batteries is carried out mainly during night. Although the capacity per charger is in the order of several kW, local voltage and wide-area frequency may be influenced, when electric power is required in a narrow area with too much concentration. Therefore, operational control for not causing such a problem is necessary.
If a real-time centralized control is realized via the Internet for such a non-urgent load as electric water heater, such a control will serve just like a load regulating power supply, as a buffer for variable electric power such as wind power, contributing to an electric power stabilization. This scheme has already been proposed by the same applicant (see Japanese Patent Publication No. 2006-353079).
Moreover, an electric car or a hybrid car at each home is equal to an electric power storage device deployed at each home. If a conversion from DC to AC is carried out depending on necessity, such car will serve as an emergency power supply (UPS) at each home for its necessary loads, which will offer a countermeasure for a power failure of a commercial electric power line.